Process for radiation cross-linking utilizing n-heterocyclic compounds with cleavable oxy substituents

ABSTRACT

ENERGY-SENSITIVE COMPOUNDS CONTAINING A HETEROCYCLIC NITROGEN ATOM SUBSTITUTED WITH AN -OR GROUP ARE CROSSLINKING AGENTS FOR POLYMERS HAVING HARDENABLE GROUPS.

United States Patent U.S. Cl. 204-159.14 11 Claims ABSTRACT OF THE DISCLOSURE Energy-sensitive compounds containing a heterocyclic nitrogen atom substituted with an OR group are cross linking agents for polymers having hardenable groups.

This application is a division of copending application Ser. No. 766,288, filed Oct. 9, 1968, now Pat. No. 3,615,- 453, issued Oct. 26, 1971.

This invention relates to a process for crosslinking polymers and crosslinkable polymer composition.

Many polymers are crosslinkable. Some crosslink without the addition of an initiator while others require a crosslinking agent. A typical crosslinking agent is formaldehyde. Frequently, crosslinking occurs immediately on the addition of the crosslinking agent. When crosslinking takes place in this manner, the entire polymer is crosslinked, i.e., in those areas of the polymer which contain the crosslinking agent. In those cases where crosslinking does not occur merely by adding the crosslinking agent, additional energy such as light or heat is necessary to initiate the reaction. It is this latter system which is most useful in the photographic area. The crosslinked polymer being harder and more insoluble than the uncrosslinked material, generally can be separated from the uncrosslinked material by treating the polymer with a solvent for the uncrosslinked polymer. Thus, when a photographic element containing a layer of the crosslinkable polymer having a crosslinking agent uniformly distributed throughout, is subjected to a pattern of activating radiation such as light or heat, the polymer is hardened in the radiation struck areas and an image can be produced merely by washing as explained previously.

It is an object of this invention to provide a novel crosslinkable composition containing a polymer and a novel crosslinking agent.

It is a further object of this invention to provide a novel process for crosslinking a polymer.

It is also an object of this invention to provide a novel process for direct electron recording.

A further object of this invention is to provide a novel class of dye mordants.

These and other objects are accomplished with crosslinkable compositions comprising a polymer having hardenable groups and a dye crosslinking agent capable of being activated by heat, pressure or radiation having one wherein:

(A) R can be any of the following:

(a) A methine linkage terminated by a heterocyclic nucleus of the type contained in cyanine dyes, e.g., those ice set forth in Mees and Jones The Theory of the Photographic Process, MacMillan 3rd ed., pp. 198232; the methine linkage can be substituted or unsubstituted, e.g.,

(b) An alkyl radical preferably containing 1 to 8 carbon atoms including a substituted alkyl radical;

(0) An aryl radical including a substituted aryl radical such as a phenyl radical, a naphthyl radical, a tolyl radical, etc.;

(d) A hydrogen atom;

(e) An acyl radical having the formula 0 JLR wherein R is hydrogen or an alkyl group preferably having 1 to 8 carbon atoms;

(f) An anilinovinyl radical having the formula wherein R is hydrogen or alkyl; or

(g) a styryl radical including substituted styryl radicals, e.g.,

wherein R is hydrogen, alkyl, aryl, amino including di alkylamino such as dimethylamino;

(B) R can be either (a) An alkyl radical preferably having 1 to 8 carbon atoms such as methyl, ethyl, butyl, etc., including a substituted alkyl radical such as sulfoalkyl, e.g., CH SO an aralkyl, e.g., benzyl or pyridinato-oxyalkyl salt, e.g., --(CH 0--Y wherein Y is a substituted or unsubstituted pyridinium salt; or

(b) An acyl radical e.g.,

(l-Ru wherein R is an alkyl radical preferably having 1 to 8 carbon atoms or aryl radical, e.g., methyl, ethyl, propyl, butyl, phenyl, naphthyl, etc.,

(C) Z represents the atoms necessary to complete a 5 to 6 membered heterocyclic nucleus including a substituted heterocyclic nucleus which nucleus can contain at least one additional hetero atom such as oxygen, sulfur, selenium or nitrogen, e.g., a pyridine nucleus, a quinoline nucleus, etc.;

(D) R, can be either of the following:

(a) A methine linkage terminated by a heterocyclic nucleus of the type contained in merocyanine dyes, e.g., those set forth in Mees and James (cited above); the methine linkage can be substituted or unsubstituted; or

(b) An allylidene radical including a substituted allylidene radical such as a dicyanoallylidene radical, an alkylcarboxyallylidene radical or an alkylsulfonylallylidene radical; and

(E) X represents an acid anion, e.g., chloride, bromide, iodide, perchlorate, sulfamate, thiocyanate, p-toluenesulfonate, methyl sulfate, tetrafluoroborate, etc.

When these compounds are exposed to electromagnetic radiation, they are decomposed by a heterolytic cleavage of the nitrogen-oxygen (N-O) bond to produce a R0+ ion, a dye base and an acid anion. The RO+ ion may be decomposed even further producing an aldehyde and H+ s CH3O+ 0104- CH=OHOH=C\ i Attached acidic mordanting group Such a mordant makes the polymer receptive to cationic dyes such as methylene blue. Cationic mordants can also be formed from the novel initiators of this invention. A typical compound and reaction are the following:

polymer Attached basic mordanting group Mordants of this type render the polymer receptive to anionic dyes.

The preferred photochemical cross-linking initiating dyes capable of being activated by heat, pressure or radiation of this invention have one of the following structures:

wherein Q Q and Q each represents the nonmetallic atoms necessary to complete a sensitizing or desensitizing nucleus containing from 5 to 6 atoms in the heterocyclic ring, which nucleus may contain a second hetero atom such as oxygen, sulfur, selenium or nitrogen, i.e., a nucleus of the type used in the production of cyanine dyes, such as the following representative nuclei: a thiazole nucleus, e.g., thiazole, 4-methylthiazole, 3-ethylthiazole, 4- penylthiazole, S-methylthiazole, 5-phenylthiazole, 4,5-dimethylthiazole, 4,5 diphenylthiazole, 4-(2-thienyl)thiazole, benzothiazole, 4-chlorobenzothiazole, 4- or S-nitrobenzothiazole, S-chlorobenzothiazole, 6-chlorobenzothiazole, 7-chlorobenzothiazole, 4 methylbenzothiazole, 5- methylbenzothiazole, 6-methylbenzothiazole, 6 nitrobenzothiazole, S-bromobenzothiazole, 6-bromobenzothiaz0le, 5-chloro-6-nitrobenz0thiazole, 4 phenylbenzothiazole, 4- methoxybenzothiazole, 5 methoxybenzothiazole, 6-methoxybenzothiazole, S-iodobenzothiazole, 6-iodobenzothiazole, 4-ethoxybenzothiazole, S-ethoxybenzothiazole, tetrahydrobenzothiazole, 5,6 dimethoxybenzothiazole, 5,6- dioxymethylenebenzothiazole, S-hydroxybenzothiazole, 6 hydroxybenzothiazole, a-naphthothiazole, ,B-naphthothiazole, fi, 8-naphthothiazole, 5methoxy-B,p-naphthothiazole, 5 ethoxy-B-naphthothiazole, 8 methoxy-a-naphthothiazole, 7-methoXy-a-naphthothiazole, 4'-methoxythianaphtheno-7',6',4,S-thiazole, nitro group substituted napaththothiazoles, etc.; an oxazole nucleus, e.g., 4-methyloxazole, 4-nitro-oxazole, S-rnethyloxazole, 4-penyloxazole, 4,5-diphenyloxazole, 4-ethyloxazole, 4,5 dimethoxazole, 5- phenyloxazole, benzoxazole, S-chlorobenzoxazole, 5- methylbenzoxazole, 5-pheny1benzoxazole, 5- or 6-nitrobenzoxazole, 5-chloro-6-nitrobenzoxazole, 6 methylbenzoxazole, 5,6-dimethylbenzoxazole, 4,6-dimethylbenzoxazole, S-methoxybenzoxazole, 5 ethoxybenzoxazole, 5- chlorobenzoxazole, 6 methoxybenzoxazole, S-hydroxybenzoxazole, 6-hydroxybenzoxazole, u-naphthoxazole, B- naphthoxazole, nitro group substituted naphthoxazoles, etc.; a selenazole nucleus, e.g., 4-methselenazole, 4-nitr0- selenazole, 4-pheny1selenazole, benzoselenazole, 5-chlorobenzoselenazole, S-methoxybenzoselenazole, 5 hydroxybenzoselenazole, 5- or 6-nitr0benzoselenazole, 5-chloro-6- nitrobenzoselenazole, tetrahydrobenzoselenazole, a-naphthoselenazole, fi-naphthoselenazole, nitro group substituted naphthoselenazoles, etc.; a thiazoline nucleus, e.g., thiazoline, 4-methylthiazoline, 4-nitrothiazoline, etc.; a pyridine nucleus, e.g., 2-pyridine, S-methyl-Z-pyridine, 4-pyridine, 3-methyl-4-pyridine, nitro group substituted pyridine, etc.; a quinoline nucleus, e.g., Z-quinoline, 3-methyl-2-quinoline, -ethyl-2-quinoline, 6-chloro-2-quinoline, 6-nitro-2-quinoline, 8-chloro-2-quinoline, 6-methoXy-2- quinoline, 8-ethoxy-2-quinoline, 8-hydroxy-2-quinoline, 4- quinoline, 6-methoxy-4-quinoline, 6-nitro-4-quin0line, 7- methyl-4-quinoline, 8-chloro-4-quinoline, l-isoquinoline, 6-nitro-l-isoquinoline, 3,4-dihydro-l-isoquinoline, 3 isoquinoline, etc.; a 3,3dialkylindolenine nucleus, preferably having a nitro or cyano substituent, e.g., 3,3-dimethyl-5- or 6-nitroindolenine, 3,3-dimethyl-5- or 6-cyanoindolenine, etc.; and, an imidazole nucleus, e.g., imidazole, l-alkylimidazole, 1-alkyl-4-phenylimidazole, 1-alkyl-4,5-dimethylimidazole, benzirnidazole, l-alkylbenzimidazole, l-alkyl- S-nitrobenzimidazole, 1 aryl-5,6-dichlorobenzimidazole, 1-alkyl-a-naphthimidazole, 1-aryl-B-naphthimidazole, 1- alkyl-S-methoxy-a-naphthimidazole, or, an imidazo[4,5- b]quinoxaline nucleus, e.g., l-alkylimidazo[4,5-b1quinoxaline such as l-ethylimidazo[4,5-b]quinoxaline, 6- chloro-l-ethylimadazo[4,5-b]quinoxaline etc., l-alkenylimidazo[4,5-b]quinoxaline such as 1-allylimidazo[4,5-b] quinoxaline, 6 chloro-1-allylirnidazo[4,S-b]quinoxaline, etc., l-arylimidazo[4,5-b]quinoxaline such as l-phenylimidazo[4,5-b]quinoxaline, 6-chloro 1 phenylimidazo [4,5-b1quinoxaline, etc.; a 3,3-dialkyl-3H-pyrrolo-[2,3-b] pyrido nucleus, e.g., 3,3-dimethyl-3H-pyrrolo[2,3-b]pyridine, 3,3-diethyl-3H-pyrrolo[2,3-b]pyridine, etc.; a thiazolo[4,S-b]quinoline nucleus; R represents an alkyl group, including substituted alkyl (preferably a lower alkyl containing from 1 to 4 carbon atoms), e.g., methyl, ethyl, propyl, isopropyl, butyl, hexyl, cyclohexyl, decyl, dodecyl, etc., and substituted alkyl groups (preferably a substituted lower alkyl containing from 1 to 4 carbon atoms), such as a hydroxyalkyl group, e.g., fi-hydroxyethyl, w-hydroxybutyl, etc., an alkoxyalkyl group, e.g., ,B- methoxyethyl, w-butoxybutyl, etc., a carboxyalkyl group, e.g., B-carboxyethyl, w-carboxybutyl, etc., an alkoxy group, e.g., methoxy, ethoxy, etc., a sulfoalkyl group, e.g., psulfoethyl, w-sulfobutyl, etc., a sulfatoalkyl group, e.g., 18- sulfatoethyl, w-sulfatobutyl, etc., an acyloxyalkyl group, e.g., ,B-acetoxyethyl, 'y-acetoxypropyl, w-butyryloxybutyl, etc., an alkoxycarbonylalkyl group, e.g., fi-methoxycarbonylethyl, w-ethoxycarbonyl butyl, etc., or an aralkyl group, e.g., benzyl, phenethyl, etc.; an alkenyl group, e.g., allyl, l-propenyl, Z-butenyl, etc., or an aryl group, e.g., phenyl, tolyl, naphthyl, methoxyphenyl, chlorophenyl, etc.;

n is a positive integer from 1 to 4; m is a positive integer from 1 to 3; g is a positive integer from 1 to 2;

L represents a methine linkage, e.g., CH=,

R and R each represent a hydrogen atom, an alkyl group (preferably a lower alkyl containing from 1 to 4 carbon atoms), e.g., methyl, ethyl, propyl, isopropyl, butyl, decyl, dodecyl, etc., or an aryl group, e.g., phenyl, tolyl, naphthyl, methoxyphenyl, chlorophenyl, nitrophenyl, etc.;

X represents an acid anion, e.g., perchlorate, tetrafiuoroborate, chloride, bromide, iodide, perchlorate, tetrafluoroborate, sulfamate, thiocyanate, p-toluenesulfonate, methyl sulfate, etc.;

G represents an anilino radical or an aryl radical, e.g., phenyl, naphthyl, dialkylaminophenyl, tolyl, chlorophenyl, nitrophenyl, etc.;

R is an alkyleneoxy radical having 1 to 8 carbon atoms in the alkylene chain including an alkylenedioxy radical and an arylenebisalkoxy radical, e.g., ethyleneoxy, trimethyleneoxy, tetramethyleneoxy, propylideneoxy, ethylenedioxy, phenylenebisethoxy, etc.

R represents either (1) an alkyl radical including a substituted alkyl (preferably a lower alkyl having 1 to 4 carbon atoms), e.g., methyl, ethyl, propyl, isopropyl, butyl, hexyl, cyclohexyl, decyl, dodecyl, alkaryl such as benzyl, sulfoalkyl such as [SI-sulfoethyl, w-sulfobutyl, w-sulfopropyl, or (2) an acyl radical, e.g.,

wherein R is an alkyl including a substituted alkyl or an aryl such as methyl, phenyl, naphthyl, propyl, benzyl, etc.,

In the above formulae Q preferably completes a pyridine, or a quinoline nucleus. Nuclei wherein Q Q and Q complete an imidazo[4,5-b]quinoxaline nucleus, or a nitro group substituted thiazole, oxazole, selenazole, thiazoline, pyridine, quinoline, 3H indole, or imidazole nucleus are desensitizing nuclei.

Typical dye crosslinking compounds used in the invention include the following:

( 1) 3-ethyl-1-methoxyoxa-2'-pyridocarbocyanine perchlorate (2) 1-ethoxy-3-ethyloxa-2'-pyridocarbocyanine tetrafluoroborate (3) 3'-ethyl-1-methoxy-2apyridothiacyanine iodide (4) 1-ethoxy-3-ethyl-2-pyridothiacyanine tetrafiuoroborate (5) l-benzyloxy-3'-ethyl-2-pyridothiacyan-ine iodide (6) 3-ethyl-1-methoxy-Z-pyridothiacarbocyanine iodide (7) 1-ethoxy-3'-ethyl-2-pyridothiacarbocyanine tetrafluoroborate (8) anhydro-3'-ethyll- 3-su1f0propoxy) -2-pyridothiacarbocyanine hydroxide (9) 1-benzyloxy-3'-ethyl-2-pyridothiacarbocycnine perchlorate (l0) 3'-ethyl-1-methoxy-Z-pyridothiadicarbocyanine perchlorate 1 1 1'-methoxy-1,3,3-trimethylindo-2'-pyridocarbocyanine picrate (12) 3-ethy1-1-methoxy-4',5-benzo-2-pyridothiacarbocyanine perchlorate 13) 1-ethoxy-3'-ethyl-4',5'-benzo-2-pyridothiacarbocyanine tetrafluorobrate (14) 1'-ethoxy-3-ethyloxa-2'-carbocyanine tetrafluorobrate (15 1'-ethoXy-3-ethylthia-2'-cyanine tetrafiuoroborate (16) 1'-ethoxy-3-et'hylthia-2'-carbocyanine tetrafiuoroborate (17) 1'-ethoxy-3-ethylthia-2'-dicarbocyanine tetrafiuoroborate 18) 1-methoxy-3-methyl-2-pyridothiaz0linocarbocyanine perchlorate (19) 3'-ethy1-1-methoxy-4-pyridothiacyanine perchlorate (20) 3'-ethyl-1-methoxy-4-pyridothiacarbocyanine perchlorate (21) 1'-ethoxy-3-ethyl-4,5-benzothia-2-carbocyanine tetrafiuoroborate (22) 2-;8-anilinovinyl-l-methoxypyridinium p-toluenesulfonate (23) l-ethyl-l-methoxy-4,5-benzothia-4'-carbocyanine perchlorate (24) 1-methoxy-2-methylpyridinium p-toluenesulfonate (25) 1-methoxy-4-methylpyridinium p-toluenesulfonate (26) anhydro-Z-methyl-l-(3-sulfopropoxy)pyridinium hydroxide (27) l-ethoxy-Z-methylpyridinium tetrafiuoroborate (28) 1-benzyloxy-Z-methylpyridinium bromide (29) l-ethoxy-2-methylquinolinium tetrafluoroborate' (30) 1,l-ethylenedioxybispyridinium dibromide (31) 1,l'-trimethylenedioxybispyridinium dibromide (32) 1,1'-tetramethylenedioxybis(Z-methylpyridinium) dibromide (3 3 1, 1tetramethylenedioxybis(4-methylpyridinium dibromide 34) 1, l'tetramethylenedioxybispyridinium dibromide (35 1, 1 '-pentamethylenedioxybispyridinium dibromide 3 6) 1-acetoxy-2- (4-dimethylamino styryl pyridinium perchlorate (37) 1-benzoyloxy-2- (4-dimethylaminostyryl) pyridinium perchlorate (3 8) 1,3-diethy1-5 1-methoxy-2( 1H)-pyridy1idene) ethylidene] 2-thiobarbituric acid (39) 3-ethyl-5-[ 1-methoxy-2( 1H pyridylidene ethylidene] rhodanine 40) 1,3-diethyl-5- 1-methoxy-2( 1H) pyridylidene) ethylidene]barbituric acid (4 1 2- 3 3 dicyanoallylidene) -1-methoxy-1,2-dihydro pyridine (42) 2- 1-methoxy-2( 1H pyridylidene ethylidene] 'benzo [b] thiophen-3 (2H) one- 1 l-dioxide 43) 3-cyano-5-[ l-methxy-2( 1H pyridylidene) ethylidene] 4-phenyl-2 H) furanone The crosslinking agents of this invention can be prepared according to an application Ser. No. 766,307 filed Oct. 9, 1968, by Jenkins, Heseltine and Mee, titled Energy-Sensitive Systems, now Pat. No. 3,615,432, issued Oct. 26, 1971.

The dye crosslinking agents described herein are capable of crosslinking any polymer containing hardenable groups. These groups can be side groups pendant from the backbone of the polymer chain or can be in the backbone itself. Also, they can be on the ends of the chain. Polymers having hardenable groups include any polymer which has groups which are capable of being crosslinked when treated with an aldehyde. Such groups include:

(a) a primary amine radical such as NH including amides such as and (b) secondary amine radicals such as NHR;

(c) hydroxyl radicals under acidic conditions, e.g., pH under about 2;

'(d) any group containing an active methylene group such as (1) a B-keto ester, e.g., acetoacetate group or (2) an u-cyano ester, e.g., cyanoacetoxy group or (3) a group containing an a-diketone moiety such as an acetoacetyl or benzoylacetyl group. Illustrative polymers include the following:

(1) poly(vinyl alcohol-co-vinyl anthranilate-co-vinyl succinate) (2) poly(ethylacrylate-co-acrylic acid-co-2-acetoacetoxyethyl methacrylate) (3) poly(methylacrylate-co-sodium-3-acryloyloxy-1- methylprop anelsulfonate-co-Z-acetoacetoxyethyl acrylate) (4) poly(methylacrylate-co-acrylic acid-co-2-methacryloyloxyethyl cyanoacetate) (5) poly(1,Z-dimethyl-5-vinylpyridinium methosulfatecom-methacryloyl-N'-cyanoacetylhydrazine) (6) poly(3-acryloyloxypropane-l-sulfonic acid, sodium salt-co-N-methacryloyl-N'-glycylhydrazine (7) poly(l,Z-dimethyl-S-vinylpyridinium methosulfateco-2-aminoethyl methacrylate) (8) poly (acrylamide-co-N-cyanoacetyl-N'methacryloyl hydrazine) (9) gelatin (l0) poly(vinylacetoacetate) The crosslinking agents used in the invention can be activated (decomposed) by various forms of energy such as (1) electromagnetic radiation including ultraviolet,

visible and infrared light, X-rays, electron beams, laser beams, (2) heat, (3) pressure, etc. When a mixture of polymer having hardenable groups and crosslinking agent is exposed to one of these forms of energy, the initiator decomposes producing an aldehyde and a dye base. The aldehyde reacts with the hardenable groups to join two different polymer chains together by crosslinks forming a composition having increased viscosity. Of course, the initiator used desirably has maximum absorption in the same regions as the activating radiation. The relative proportions of the polymeric material and the crosslinking agent can be varied as desired or as conditions may require, but ordinarily the proportions thereof in the mixture will be at least about 0.1% and generally within a range such that 0.1 to 10% by weight of the aldehyde produced on fragmenting the original compound will be present after its decomposition, and preferably 1.0 to 7.0% by weight of such aldehyde in the total composition (including polymer and original compound).

The preferred sources of energy include visible light and electron beams. Strong light is not necessary, a 150 Watt Xenon arc lamp at a distance of less than a foot being very suitable since at relatively low intensities the photochemical crosslinking influence of the initiators of this invention is sufficiently strong. When electron beams are used, the intensity of the beams can range from 1 1w. to kv. with 15 kv. generally being suflicient.

The time of exposure is not critical but is somewhat dependent upon the amount of crosslinking agent present and the intensity of the light source. Relatively large amounts of crosslinking agent and strong light sources require shorter times of exposure. Periods for exposure can range from a fraction of a second to several hours. However, for most applications 1 second to 1 hour is sufficient.

The crosslinkable compositions of this invention are useful in the reproduction of images in that their exposure to light or other forms of energy can cause insolubilization of the crosslinking composition. Thus, when a layer of one of these compositions, initially soluble, is applied to a support and exposed photographically, the exposed areas become insoluble.

The invention is useful for the formation of elements wholly made from these compositions. The present invention also makes possible the formation of coated printing films on any base by the deposition or coating by conventional means of films or coatings of the subject novel crosslinkable compositions. Typical bases or supports are metal sheets (e.g., copper, aluminum, zinc and magnesium), paper, glass, cellulose acetate butyrate film, cellulose acetate film, poly(vinyl acetal) film, polystrene film, polycarbonate film, poly(ethylene terephthalate) film, polyethylene-coated paper, nylon and metal screens.

The base or support is typically coated with a solution of the polymeric material in a suitable solvent, this solution containing dissolved or homogeneously dispersed therein, an energy-sensitive crosslinking initiator as described hereinabove whereupon the solvent or solvent mixture is eliminated by known means such as evaporation, leaving a coating of the photosensitive mixture upon the base or support. Thereafter, the dried photosensitive coating can be imagewise exposed to actinic light rays or other suitable energy source.

When the support material carrying the photosensitive composition is light-reflecting, there can be present, e.g., superimposed on said support and adherent thereto or in the surface thereof, a layer or stratum absorptive of actinic light in order to minimize reflectance from the combined support of incident actinic light.

If the crosslinkable composition is water-soluble, water can be used as the solvent in coating the support. If waterinsoluble compositions are used, organic solvents, mixtures of organic solvents or mixtures of organic solvents and water can be used. Suitable solvents can be readily ascertained by one skilled in the art.

The elements formed wholly of or coated with the photosensitive composition are useful in photography, photomechanical reproduction processes, lithography and intaglio printing. More specific examples of such uses are offset printing, silk screen printing, duplicating pads, manifold stencil sheeting coatings, lithographic plates, relief plates, and gravure plates. The term printing plates as used herein is inclusive of all of these.

A specific application of the invention is illustrated by a typical preparation of a printing plate. In this application a plate, usually of metal, is coated with a film of the crosslinkable composition. Alternatively, any suitable support can be coated with a film of the composition. The surface of the plate is then exposed to visible light through a transparency, e.g., a positive or negative (consisting of opaque and transparent areas). The light induces the decomposition of the crosslinking agent to a dye base and an aldehyde, and the aldehyde in turn crosslinks the polymer in the areas of the surface beneath the transparent portions of the image causing these portions to become insoluble, whereas the areas beneath the opaque portions of the image retain their pre-exposure solubility. The soluble areas of the surface are then removed by a solvent, and the insoluble, raised portions of the film which remain serve as a resist image, wherein a relief plate is formed by etching the exposed base material. The plate carrying the insolubilized raised portion, i.e., the relief image, can also be inked and used as a relief printing plate directly in the customary manner.

The thickness of the photosensitive layer is a direct function of the thickness desired in the relief image and this will depend on the subiect being reproduced and particularly on the extent of the non-printing areas. In the case of half-tones the screen used is also a factor. In general, the thickness of the photosensitive layer may vary from 0.001 mm. to 7 mm. Layers ranging from 0.001 to 0.70 mm. in thickness may be used for halftone plates. Layers ranging from about 0.05 to about 1.50 mm. in thickness will be used for the majority of letterpress printing plates, including those wherein half-tone and line images are to be combined.

The solvent liquid used for washing or developing the printing plates made from the photosensitive composition should have good solvent action on the unexposed areas, yet have little action on the hardened image or upon the base material, the antihalation layer, or the subbing layer with which the photosensitive composition may be anchored to the support.

The crosslinkable compositions of the invention show many advantages over the known photosensitive compositions. These compositions can be crosslinked by exposure to any form of light or other energy source simply by selecting a crosslinking agent which is sensitive to the particular form of energy employed. For example, the dye crosslinking agents can be made to have maximum light absorption over wide portions of the visible spectrum facilitating several types of exposing means. Mixtures of such dyes can also be used to facilitate imagewise exposmg.

The photosensitive crosslinking compositions are suitable for other purposes in addition to the printing uses described above, e.g., as ornamental plaques or for producing ornamental effects; as patterns for automatic engraving machines, foundry molds, cutting and stamping dies, name stamps, relief maps for braille, as rapid cure coatings, e.g., on film base; for the production of sound tracks on film; for embossing plates, paper, etc.; and in the preparation of printed circuits.

The following examples are included for a further understanding of the invention.

EXAMPLE 1 A composition containing gelatin and compound 24 in an amount suflicient to produce 3.0% aldehyde by weight of the total composition is coated on a poly(ethylene 10 terephthalate) film support at a thickness of 6;. The element is exposed to a transparency having opaque and transparent areas with a 140 watt ultraviolet lamp placed 3 inches away from the surface of element casing crosslinking to occur in the exposed areas. After exposure, the element is washed with water. The unexposed areas washolf leaving only an image formed by the exposed hardened areas. This procedure is repeated for compounds 22, 25, 26, 27, 29, 32 and 33 and similar results are obtained.

'EXAMPLE 2 Example 1 is repeated except varying amounts of compound 24 are employed to show the effect on crosslinking for dilferent concentrations of crosslinking agent. The elements are swollen by immersing them in water for 3 minutes. The extent of swelling or percent swell is an indication of the amount of crosslinking which has occurred, smaller amounts of swelling being indicative of greater amounts of crosslinking. The results are set forth in Table I below.

TABLE I Percent aldehyde relative Compound to dry Percent No. vehicle swell Blank 0 580 32 1 302 32 2 265 32 6 EXAMPLE 3 Example 1 is repeated except compound 34 is used in place of 32 and poly(vinylacetoacetate) is used as the vehicle in place of gelatin. After washing with water, a good relief image is obtained.

EXAMPLE 4 This example illustrates the preparation of a lithographic plate. Compound 24 is mixed with gelatin at a level calculated to produce theoretically 6% of formaldehyde with respect to dry weight of gelatin. The composition is coated on an anodized aluminum sheet at a thickness of 0.002 in. The dried coating is exposed for 15 minutes to the light from a 140 watt Hanovia ultraviolet lamp through a definition chart. The exposed plate is washed with 85 F. water for 10 minutes and dried. The sheet is placed on a lithographic printing press and a good press copy is obtained.

EXAMPLE 5 The crosslinkable compositions of this invention are also useful in simple transfer processes. A coating of compound 24 (calculated to produce 6% formaldehyde) in gelatin is coated on a fiuorinated hydrocarbon resin film (Teflon) support at a thickness of 0.004 in. The dried material is exposed, as above, through an appropriate negative. The exposed sample is dipped in a warm, silver nitrate-urea solution. The sample is removed from the solution and placed in contact with a Verifax receiving sheet, separated, and the transferred image is developed in Kodak D72 Developer. A good reproduction of the original is obtained.

EXAMPLE 6 Production of dye mordants with simultaneous hardening Compounds with ionic or cationic groups attached, when fragmented by energy, produce an aldehyde with a potential mordanting group. A gelatin silver halide emulsion coating containing compound 26 is prepared so that 3% of the propionaldehyde-3-sulfonic acid would be expected if reaction occurred. The coating is exposed through a mask with the emulsion side toward a 150 watt xenon are lamp placed within 1 inch of the opening in the lamp housing. The test pattern is cooled with a stream of nitrogen during a 95 min. exposure. The 1% inch square test strip is hardened in a 2% succinaldehyde prehardening bath for 1 min. and rinsed under a flow of distilled water at 26 C. for 15 min. The test square is then dyed with a solution of methylene blue prepared by placing 0.4 g. of methylene glue in 10 ml. of water, slurrying for 10 min. and filtering. A definite mordanting is noted in the exposed areas. The strip upon standing in distilled water overnight at room temperature, retains the dyeing of the exposed area.

EXAMPLE 7 A 4 /2 by 6 /2 in. coating of poly(vinylacetoacetate) on Estar is prepared containing an amount of compound 33, such that if complete reaction occurred, 6% succinaldehyde, with respect to dry polymer, would be expected. This coating is exposed through the Estar base using a combined definition chart, resolution chart, and step wedge coating on glass for hr. and 5 min. (The reason for this long exposure time is that the glass and film base combined present an optical density at 2500-2700A in excess of 8.0). The coating is then dyed for -15 sec. in a 10% solution of 1,8-dihydroxy-2-(6,8-disulrfonaphthyl 2 azo) 3,6 disulphonaphthalene, tetra sodium salt, washed with running water, first at 85 F., and then at 91 F. for a total of 20 min. Dyeing occurs preferentially in the exposed areas substantiating a mordanting effect.

EXAMPLE 8 Example 7 is repeated except the crosslinking agent employed is compound 32 and the dye used is 1,5-disulfomethylamino 3,7 disulfo 4,8 dihydroxyanthraquinone tetrasodium salt. Similar results are obtained.

EXAMPLE 9 Direct electron recording Energy other than light can be used to produce fragmentation of the novel crosslinking agents of this invention. A set of strips is coated with a composition containing gelatin and sufiicient amounts of crosslinking agent to produce 6% aldehyde relative to the dry vehicle. The crosslinking agents employed are compounds 24, 32 and 33. The strips are then subjected to a graded series of exposures to kilovolt electrons. The strips are then washed with water and inspected for differential hardening. Each of the strips contained hardened areas.

EXAMPLE 10 In order to determine the mordanting effect, each of the exposed strips are bathed in the dye solution used in Example 7. Dyeing occurs preferentially in the exposed areas. When the dye strips are placed in distilled water overnight, the dye is not removed.

The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. A process which comprises providing a polymer composition comprising a polymer having hardenable groups and a crosslinking agent capable of being activated by electromagnetic radiation having the formula:

12 wherein:

(A) R is selected from the group consisting of:

(a) a methine linkage terminated by a heterocyclic nucleus of the type contained in cyanine 5 dyes,

(b) an alkyl radical, (c) an anilinovinyl radical, (d) a hydrogen atom, (e) an aryl radical,

10 (f) an aldehyde group and (g) a styryl radical;

(B) R is selected from the group consisting of:

(a) an alkyl radical and (b) an acyl radical;

15 (C) X is an acid anion; and

(D) Z represents the atoms necessary to complete a 5 to 6 membered heterocyclic nucleus;

and subjecting the polymer composition to a form of electromagnetic energy sufficient to effect crosslinking of said polymer.

2. A process which comprises providing a polymer composition comprising a polymer having hardenable groups capable of being cross-linked when treated with an aldehyde and a crosslinking agent capable of being activated by electromagnetic radiation and subjecting said polymer composition to a form of electromagnetic energy sufiicient to effect crosslinking of said polymer, said crosslinking agent having a formula selected from the group consisting of:

wherein:

(A) Q Q and Q each represent the nonmetallic atoms necessary to complete a 5 to 6 membered heterocyclic nucleus;

(B) n is a positive integer from 1 t0 4;

(C) m is a positive integer from 1 to 3;

(D) R is an alkyleneoxy radical having 1 to 8 carbon atoms in the alkylene chain;

(E) g is a positive integer from 1 to 2;

(F) X is an acid anion;

(G) L is a methine linkage;

(H) R is selected from the group consisting of an alkyl radical and an acyl radical;

(I) R and R are each selected from the group consisting of an aryl radical, a hydrogen atom and an alkyl radical;

(J R is selected from the group consisting of an alkyl radical, an alkenyl radical, an aryl radical and an alkoxy radical; and

(K) G is selected from the group consisting of an anilinovinyl radical and an aryl radical.

3. The process of claim 2 wherein the form of electromagnetic energy is selected from the group consisting of visible, ultraviolet, infrared and electron radiation.

4. The process of claim 2 wherein the hardenable groups of the crosslinkable polymer are selected from the group consisting of:

(a) a primary amine radical,

(b) a secondary amine radical,

(c) a hydroxyl radical under acidic conditions and (d) a radical containing an active methylene group.

5. A process which comprises providing a polymer composition comprising a polymer having hardenable groups capable of being cross-linked when treated with an aldehyde and a crosslinking agent capable of being activated by electromagnetic radiation having the formula:

(A) R is selected from the group consisting of:

(a) a methine linkage terminated by a heterocyclic nucleus of the type contained in merocyanine dyes and (b) an allylidene radical;

(B) R is selected from the group consisting of:

(a) an alkyl radical and (b) an acyl radical; and

(C) Z represents the atoms necessary to complete a 5 to 6 membered heterocyclic nucleus; and subjecting the polymer composition to a form of electromagnetic energy sufficient to effect crosslinking of said polymer.

6. A process which comprises providing a polymer composition comprising a polymer having hardenable groups capable of being cross-linked when treated with an aldehyde and a cross-linking agent capable of being activated by electromagnetic radiation to produce an aldehyde, having the formula;

wherein:

(A) R is selected from the group consisting of:

(a) an alkyl radial and (b) an acyl radical (B) Z represents the atoms necessary to complete a pyridinium nucleus; (C) R is a pyridinium nucleus substituent selected from the group consisting of:

14 (a) a methine linkage terminated by a heterocyclic nucleus of the type contained in cyanine dyes, (b) an alkyl radical, (c) an anilovinyl radical, (d) a hydrogen atom, (e) an aryl radical, (f) an aldehyde group and r (g) a styryl radical; and

(D) X is an acid anion, and subjecting the polymer to sufiicient electromagnetic energy to effect cross-linking of said polymer.

7. A process according to claim 6 in which Z represents the atoms necessary to complete a pyridinium nucleus and R occupies position 2 or 4 in said nucleus.

8. A process according to claim 6 in which said crosslinking agent is a l-alkoxy pyridinium compound which is ring substituted in the 2 or 4 position by an alkyl substituent having from 1 to 8 carbon atoms.

9. A process which comprises providing a polymer composition comprising a polymer having hardenable groups capable of being cross-linked when treated with an aldehyde and a cross-linking agent capable of being activated by electromagnetic radiation having the formula wherein:

(A) R is selected from the group consisting of:

(a) an alkyl radical and (b) an acyl radical;

(B) Z represents the atoms necessary to complete a 1,2-dihydropyridine nucleus; and

(C) R is a 1,2-dihydropyridine nucleus substituent selected from the group consisting of:

(a) a methine linkage terminated by a heterocyclic nucleus of the type contained in merocyanine dyes and (b) an allylidene radical, and

subjecting the polymer to suificient electromagnetic energy to effect cross-linking of said polymer.

10. A process according to claim 9 in which Z represents the atoms necessary to complete a pyridine nucleus and R occupies position 2 or 4 of said nucleus.

11. A process according to claim 9 in which said crosslinking agent is a l-alkoxy pyridine compound which is ring substituted in the 2 or 4 position.

References Cited UNITED STATES PATENTS 2,991,285 7/1961 Feely 260-827 3,615,453 10/1971 Jenkins et a1.

MURRAY TILLMAN, Primary Examiner R. B. TURER, Assistant Examiner US. Cl. X.R.

( CERTIFECATE 0F CORRECTION Patent No. 3,699,025 Dated October 17, 1972 Inventor) Philip W. Jenkins Donald W. Heseltine and John D. I

It is certified that e rror appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 11, line 67', Claim 1, After the word "groups" the following-should, be inserted "capable of belng cross-linked when treated with an aldehyde-. columnls, line 20', Claim 5;

z l J\\ M /Z.\ r 1 should read I I N/ Column 14, line '5, Claim 6, "an'ilgvi'nyl" should read --anilinovinyl.-

n Sealed this 27th day of November 1 (SEAL) Attest:

EDWARD M.FLETCHER,JR. RENE D. TEGTMEYER Atte'fiting Officer Acting Commissioner of Patents 

